1. Field of the Invention
The present invention relates to a machine for manufacturing a material sheet, e.g., a paper or cardboard sheet. The machine may include with a dryer section having at least one dryer group with a plurality of dryer cylinders. The plurality of dryer cylinders may be positioned such that the centers of a first plurality dryer cylinders are arranged on an upper level and that the centers of a second plurality of dryer cylinders are arranged on a lower level spaced a distance from the upper level. The machine may also include a top felt assigned to at least one of the dryer cylinders of the upper level and a bottom felt assigned to at least one of the dryer cylinders of the lower level to guide the material sheet along a meandering (or winding) run through the dryer group. The material sheet may be guided between the top felt and the bottom felt in at least one transition area located between the dryer cylinders.
2. Discussion of Background Information
Machines similar in general to the type described above are known in the art, however, these machines consist of dryer sections with at least one dryer group with a number of dryer cylinders positioned on two levels spaced at a distance from each other. Dryer groups of this type are commonly referred to as double-row dryer groups. A felt for guiding the material sheet is assigned to each of the top and the bottom cylinder rows. The material sheet runs through the dryer group alternatingly, i.e., the sheet is alternately guided around a dryer cylinder of the upper row and a dryer cylinder of the bottom row. The material sheet runs through a free stretch between the dryer cylinders, i.e., in which the sheet is not guided the felt belts. A disadvantage of this arrangement is that the material sheet can shrink freely when in the free stretches. Further, because shrinkage on the sheet edges is greater than in the middle of the sheet, this shrinkage results in a material sheet that exhibits different characteristics across its width.